Rotary expansible chamber devices – With mechanical sealing
Reexamination Certificate
2000-07-18
2001-09-11
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
With mechanical sealing
C418S201100, C277S351000
Reexamination Certificate
active
06287100
ABSTRACT:
In dry-running rotation screw compressors, no oil for lubrication, cooling and sealing is introduced between the rotors into the sealing space. The ribs of the main runner and the nuts of the secondary runner form a “dry” engagement which nevertheless achieves a seal between them. Such screw compressors are particularly suited because they allow the absence of oil in the seal space in applications in pneumatic conveyor installations, for example, for filling and emptying silos, tanks, tanker vehicles and similar instruments with bulk goods. In particular, in the pneumatic conveyance of sensitive goods such as foods or chemicals it is important that the conveyance air stream is free, to a high extent, of oil particles.
In the case of dry-running screw rotors, an appropriate seal of the shaft peg must be used to prevent oil from the oil-lubricated bearings of the shaft pegs to reach the sealing space as a result of leakage along the shaft pegs. It is already known from GB A 1189856, to arrange on the shaft peg of rotation screw compressor, next to each other, a conventional sealing ring and an oil sealing ring, which are separated from each other by an annular space which is connected to the external air. However, because of the high level of abrasion, ordinary sealing rings are unsuited for establishing seals of rapidly rotating shaft pegs, which can reach circumferential speeds of 55-150 m/sec. On the other hand, it is known to use two adjacent, contact-free, labyrinth seals to seal the shaft peg of a dry-running rotation screw compressor; of the labyrinth seals, the one located closest to the oil-lubricated bearing is in the form of an oil return threading. However, it has been shown that such contact-free labyrinth seals cannot always reliably prevent the leakage of oil along the shaft peg to the seal space, particularly if there is high pressure differential on the suction-side of the seal. From DE A 24 41 520, a shaft seal is known for a screw rotor seal with water injection, which presents several sealing hoops surrounding the rotor pegs, and located between the annular chambers, of which one is applied to the ring chamber with the gas densified by the compressor, as a barrier gas, and the other ring chamber is a drainage chamber for bearing oil drainage. The sealing hoops are labyrinth seal hoops, of which one also can be a contact seal. This shaft seal is a dynamic seal, which uses pressurized barrier gas, which must be shunted from the conveyor gas stream of the compressor, and which thus entails an output loss.
It is an object of the invention to provide a sealing arrangement which works without barrier gas, which presents a particularly high sealing effect and, nevertheless, good abrasion resistance, for a shaft peg of a dry-running rotation screw compressor.
For achieving the object, the invention provides a sealing arrangement on a rotor shaft peg of a dry-running rotary screw compressor for establishing a seal between the rotor and an oil-lubricated bearing of the shaft peg. The sealing arrangement has a labyrinth gap seal closer to the rotor and a lip seal ring closer to the bearing and in between an annular space with a ventilation opening towards the atmosphere. The shaft peg carries a bearing ring made of hardened material which cooperates with the lip sealing ring.
REFERENCES:
patent: 2018372 (1935-10-01), Mason
patent: 5354071 (1994-10-01), McClure
patent: 5501469 (1996-03-01), Ducugnon et al.
patent: 6095780 (2000-08-01), Ernens
patent: 5-18375 (1993-01-01), None
Achtelik Carsten
Gilfert Karl-Heinz
Heinz Arno
Murmann Walter
GHH-Rand Schraubenkompressoren GmbH
Michael & Best & Friedrich LLP
Vrablik John J.
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